Gear lapping machine



May 12, 1959 Filed Feb. 15, 1955 D. J. WATT GEAR LAPPING MACHINE 5Sheets-Sheet 1 i5 1a 5 i 2 gg fi s 5 11:11:11 I i :3 LQZ-ZEII 'u. 1 I...=a 2Q 12 z A! J 15 4 /"I I I I W INVENTOR.

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GEAR LAPPING MACHINE 3 Sheets-Sheet 2 Filed Feb. 15, 1955 INVENTOR gg/nil Joseph Vail May 12, 1959 D. J. WATT GEAR LAPPING MACHINE FiledFeb. 15, 1955 3 Sheets-Sheet 3 2 m'roz/v am.

United States Patent GEAR LAPPING MACHINE David Joseph Watt, Clarence,N.Y., assignor to Farrel- Birmingham Company, Inc., Butfalo, N.Y., acorporation of Connecticut Application February 15, 1955, Serial No.488,309

6 Claims. (11. 51-26) The present invention relates to a gear lappingmachine and aims to provide certain improvements therein. The lapping ofgears so that they will properly mesh with one another and therebyoperate most efliciently f and quietly has been, up to the present,considered an art. In practicing this art, operators of lapping machinesapplied pressure between a pinion and a gear to be lapped v by thesimple procedure of progressively advancing, by ffscrew means, thepinion and gear into intimate engagement with each other by closing thedistance between the pinion shaft and the gear shaft. The [forcedeveloped by the application of screw pressure resulted in a deflectionor spring in the lapping mechanism or lapping setup, hence, neitherexact pressures nor exact cycling were ever known and the results weredependent upon the operators skill and attention devoted to the lappingoperation. Moreover, lapping times could be extensive or relativelyshort, and the lost time, added expense incident to such .lost time, andthe questionable accuracy obtained has caused many gear manufacturers toabandon lapping as a finishing procedure in gear manufacture.

The primary object of the present invention is to eliminate theuncertainties incident in the art of gear lapping. A further object ofthe invention is to transform gear lapping from an art to a science.

A still further object of the invention is to provide a machine forlapping gears under predetermined pressure between the mating gear andpinion and stopping such flapping action when the desired centerdistance between j the gear-set is reached.

A still further object of the invention is to rely upon L a controllablefluid pressure to apply the desired constant predetermined pressurebetween the pinion and the gear being lapped.

A still further object of the invention is to provide a "machine of thecharacter set forth which will provide an inspection medium for checkingany pitch line run-out detail.

Patented May 12, 1959 Figure 1 is a top plan view of a machine embodyingthe invention.

Fig. 2 is a side elevational view of the machine shown in Fig. 1.

Fig. 3 is a partial top plan view, on an enlarged scale, of the pinionmounting and pressure-applying means therefor.

Fig. 4 is a side elevational view of the parts illustrated in Fig. 3.

Figs. 5 and 6 show views corresponding respectively to Figs. 3 and 4, ofanother embodiment of the invention.

Referring first to Figs. 1 to 4 of the drawings, the reference numeral10 indicates a machine bed having transverse ways 11, upon which aremounted a pair of spaced pedestal bearings or center heads 12 and 13adapted to be adjustably positioned by pinion-operable means 15 and tobe clamped to said bed by conventional means such as locking bolts 14and 16. Also formed on said bed 10 is a pair of longitudinally-extendingways 17, 18, upon which is slidably movable a saddle 19 operable by asaddle screw 20 controlled by a hand wheel 21.

The pedestal heads 12 and 13 are herein shown fitted with centers 22 and23, respectively, adapted to rotatably support a shaft 24 upon which ismounted a gear 25 to be lapped. It will be obvious, however, that thegear, on its journals, may be mounted in the pedestal heads.

The saddle 19 is formed with transverse ways 26 upon which are mounted apair of pedestal bearings, or center heads 27 and 28 which areadjustable toward and away from each other by pinion-operable means 29and adapted to be secured to said ways by locking bolts 30 and 31. Alsoformed on the saddle 19 is a transverse way 32 upon which a drive motor33 is adjustably mounted. The pedestal heads 27 and 28 as herein shownare provided with centers 34 and 35, respectively, adapted to rotatablysupport a shaft 36 upon which a pinion 37 is mounted. As in the case ofthe gear 26, the pinion 37 may be mounted in the pedestal heads on itsjournals.

The pedestal heads 27 and 28 are substantially the same and only one ofsaid heads will be described in Each pedestal head 27 and 28 consists ofa lower part 38 adapted to be clamped to the saddle, and an upperpivoted or rockable head 39. The part 38 is formed with a pair ofaxially spaced bearings 38 and with an extended base or foot portion,which is hollowed spaced from and extending parallel to its axiallyspaced 'bearings, is formed with an overhanging or reentrant of ,apinion and gear set and as an eccentricity check upon gearsets bothbefore and after lapping.

The foregoing and other objects of the invention not specificallyenumerated are accomplished by mounting a pinion on an axis which isparallel to and movable toward and away from the axis of a gear;applying a constant predetermined pressure, preferably through fluidpressure operated means, to press the pinion and gear into engagement;providing means for adjusting the desired center distance between thepinion and the gear; and providing stop means which will prevent furthermovement of the pinion toward the gear when the desired center distancebetween the pinion and gear is reached. The invention also embodies theuse of instruments which will enable the pitch line run-out to bechecked during and after the lapping operation.

The invention, which embodies a novel machine including the variouscombinations and sub-combination of parts, will be fully understood fromthe detailed descripition which follows, when considered in connectionwith I the accompanying drawings, wherein:

flange 42, the under face of which provides a stop shoulder 43 for apurpose presently to be described. The pivoted or rockable head 39 isformed with a lower central bearing portion 39 mounted on anintermediate portion of a shaft 40, the ends of which shaft are mountedin the axially spaced bearings 38 in the part 38 and with upper bearingportion 39" for supporting the center 34 and with an extended base orfoot portion 44 of a width to fit within the hollowed portion 41 of part38. The foot portion 44 is of a length to engage beneath the stopshoulder 43 on the flange 42. The base or foot portion 44 is of athickness to have limited movement within the hollowed part 41 as thehead 39 pivots or rocks about the shaft 40. Mounted in the overhangingflange 42 is an indicator 45, the contact member of which is adapted toengage the top surface of an upstanding enlargement 46 on the footportion 44 and to register when the enlargement 46 and stop shoulder 43are out of engagement, the amount of such disengagement. At times it maybe desirable to lock the rockable head 39 against movement relative tothe part 38 and, for. accomplishing this, a pair of locking screws47-eachhaving an operating handle 48, may "be turned to engage threadedsockets 49 in the enlargement 46. The part 38 is formed with a pair ofcylindrical sockets 50 extending inwardly from the bottom of thehollowed outportion 41, .and mounted in each of said sockets is a piston51 adapted to press against the under side of the foot portion 44 tourgethe top surface of the enlargement 46 into abutting relation with thestop shoulder 43 when said piston is actedupon by' fluid pressureadmitted to the socket 50 from a'flu'id pressure system. As'hereinshown, the fluid pressuresystem is of thehydraulic type and comprises anaccumulator 52 adapted to be charged by a hand pump 53" having a.pressure gauge 54, there being a conduit 55 leading-fromthe-accumulator to a distributor-head 56 from which conduits 57, 58, 57and 58 lead to the cylindrical sockets 50.

Y The pressure to be employed in'thefluid pressure system will begoverned by experience and depends uponthe .size of gear tobe lapped.For each diametral pitch of gear-set that is to be lapped, apredetermined unit pressure (or desired pressure per: inch of face) willbe determined For example, if it beassumed that a' 3 DP gear having aface width. of 12" is to be lapped and it has been determinedthat themost desirable unit pressure is -40 pounds, vunder these conditions the:hand pump 53 will be operated to apply pressure tliroughthe accumulator52 to the four pistons 51 until .the pressure {gauge 54 reads 480 lbs.force, or40 12. i It will readily be seen that the pressure can .beadjusted to any predetermined unit pressure for agiven diametral pitchofgear, times. the face width of the gear.

For. indicating the center-distance .betweenthe subject gear and thelapping gear, a scale 59'is mounted on the :bed for cooperationwith avernier 60 mounted Hon-the saddle and with a cooperating. indicator 61.mounted on the saddle.

Operation The gear-set to be lapped, consisting or a'gear '25 and pinion37, will be mounted on the centers, or bearings for the gear and pinionjournals supported in the pedestals 1 2, '13, and."27,28, respectively,and a predetermined fluid pressure will beapplied to the pistons "'51 inthecylindrical sockets 50to force the top surface of the enlargements46. against the stop -shoulders"43. The gear and its. mating pinion willthenbe checked [I for parallelism of journals aridface.

The, pinion "37 will then be moved toward the gear byactuatingthesaddlescrew 20 through the hand whe'el"21 until-the l indicator'45 movesslightly fromits zero reading. 'This will indicate that the gear-set ismeshed with'zero back- 1 lash. The operator will 'thenread theVernier-scale 59, 60, and determine the .amount that itis: necessary toadvance the pinion toward the, gear'to obtain the "final'desired lappedgear centers. "For descriptive purpose, let it be assumed that the'gearcenters of the meshed jgear'set is @010 wider than the'finally'. desiredlapped centers. Knowing the amountthat the centers are in excess ofdesired specifications by'a certain amount, the indicator 61 can be setto this amount. The operator -will then set .the indicator 61 to read.010" plus, and

will then advance the saddle l9 through the. hand wheel "'21 and saddlescrew'20 until'the indicator 61- reads zero, .at which time the scale59,60, will read the'desir'ed lapped gear center distance. Thisindicator'61 is mere- 'ly a device used to allow' the operator tocontrol his -action as he manipulates-the hand wheel 21 to advance thepinion saddle 19 and heads 27 and'28 to the desired center distances.'In .other words, by again turning hand wheel 21.he can make theindicator'61 return" to zero by moving the pinion saddle and headassemblytoward ;the gear or away from indicator 61. "If desirablep he"can again check thevernier scale"59, '60, by walking around the 'sideof the mechanism to see that theffinished Icenter distance correspondstothe designedspecification.

enlargement 46 on the swivel head39 will abut against pressureagainst'the gear-set teeth, at which-time the lapping cycle iscommenced, the pinion journal or-'shaft 36 being rotated bythedrive-motor 33- and-belt 63. A suitable lapping compound will, ofcourse, be applied to the gears during'the' lapping' operation. It Willbe readily seen that as material is removed from the gear and pinion bythe lapping action, continuous predetermined. pressure will be appliedto the geariteeth until suchwtimeasthe desired center distance isreached. Whenthe desired lapped center distance is reachedfthe the stopshoulder v43, preventing any further advancement of. the pinion towardthe. gear, thus removingthe predetermined. lapping pressure. 'When thisoccurs, the

lapping machine may be shut down.

'The indicator 45may also serve to check any pitch line run-out in thegear and the pinion and will serve asan eccentricity checkof gear-sets,both before and after. lap.-

. ping, without the necessity of a separate set-up in acheck- -ingmachine for. this purpose.

Pitch line run-out will be -shown:-on. indicator 45, which, if thereispitch line runout, should-fluctuate to about twice the amount ofithepitch: line run-outat-the start-and can beobserve'd atfthe.'discretion.of the operator.

It is obvious that the. lapping will .undoubtedly follow and perpetuatevthe pitch line run-out until the end of the lapping cycle, when theproper center distance is being approached, at which time the enfluidpressure force to be transmitted to the pinion andgear largement 46 onthe head 39 will contact the stop shoulder 43 which will absorb theforce exerted by thefluidpressure mechanism. If there is pitch linerun-out, thestop will be contacted during the time that the pitchline islow, removing the force between the lapping gear and subject gear. Whenthe pitch line run-out becomes high, the-pressure between the subjectgear and the lappingv gear will separate the enlargement 46 from thestop, causing'the in mesh. This forces the gear to lap and removev metalat the high pointnon the pitch' line run-out-whilethe tendency to removemetal at the low point will be reduced to near zero. During this timethere will be a continued period where the fluctuations in indicator45,approa'ch' a condition of longerand longer periods of no fluctuation.

.Assoon as the needle on the indicator 45 ceases to fluctuate, thelapping cycle has been completed, the, gears may be cleaned of lappingcompound, the fluid pressure can be reduced andthe-saddle advanced anadditional few'thousandths, so that the gears may run together and apitch line line run-out check made of the finished lappedgears. At thispoint it would be necessary for the operator to continuously observe theindicator 45.

In-the embodiment of the invention shown in Figs. 5 and 6 the pivotshafts 40a for the right and left side of the pinion have been loweredand incorporated in a H single pedestal bearing, or center head'27A inwhicli the 58 of'Figs. l to 4. part pedestal 27Ais formed withtransverse ways 64 on top surface of the enlargement 46a whichcontrols'the maximum rotation about the pivot shaft 40a has been -movedto act against a shoulder stop 43a formed on the saddle 19. "The lock47a and locking handle-48a and theindicator 45a have been movedcorrespondingly. In this embodiment the-saddle 19 is formed withcylindrical sockets 50a for the operating pistons, and conduits 55a, 57aand 58a correspond in function to the conduits 55 to The lower member38a of thetwowhich the upper members 39a, which support the pinion,

are adjustably mounted. The difierence between this embodiment of theinvention and that shown in Figs. 1 to 4 is that a strong structuralmember 38a which extends completely under the pinion, ties both pinionsupports 39a together, requiring unitary pivoting of both said supports.This provides a means of pre-assembly of the mating gear and pinionshafts and insures maintaining parallelism between said shaftsthroughout the lapping cycle. The operation of this embodiment isprecisely the same as that of the mechanism shown in Figs. 1 to 4,although the performance may be slightly diiferent.

In cases where the straightness of the teeth across the face has notbeen manufactured correctly, whereby to provide a concentration of forceon one side of the contact with no contact on the other side, theprocedure outlined above would, of course, apply considerably norepressure in the contact for the same fiuid pressure as used previouslyfor the mechanism shown in Figs. 1 to 4. This would, in efiect, producemore rapid lapping where the load is concentrated in the pinion to giveadditional correction more rapidly at the start of a lapping cycle, withthe finish lapping similar to that accomplished by the embodiment shownin Figs. 1 to 4.

In cases where previous processing of gears has pro duced toothstraightness or helix trueness, so that true distribution is obtainedfrom one side of the face to the opposite, then the mechanism shown inFigs. 1 to 4 would be preferable, since small advances of each pedestalwill be allowed to suit the lapping requirements of the mating gear andpinion and maintain constant tooth pressure throughout the lappingcycle. This procedure is also preferable for extremely rapid lapping,wherein it is desirable to apply pressure approaching, but notexceeding, the crushing pitting strength of the gear teeth being lapped.The crushing pitting strength refers to a fatigue characteristic whichresults in small, inverted cones of material extracted from the geartooth at the pitch line. This phenomenon occurs when the Hertz stressfor allowable sub-surface shear is exceeded.

The embodiment shown in Figs. 5 and 6 would allow more rapid correctionutilizing lower overall pressures wherein tooth straightness or helixtrueness required improvement. It will thus be seen that each of theembodiments of the invention has advantages in the control of thelapping procedures in converting such procedures from an art to ascience.

Although there has been shown and described two embodiments of theinvention applied to the lapping of spur gears, it is to be understoodthe invention is applicable to helical and herringbone gears and thatthese specific constructions disclosed may be modified within the rangeof engineering skill without departing from the spirit of the inventionas hereinafter defined.

What I claim is:

1. A gear lapping machine comprising a bed having supports for rotatablymounting a gear, a saddle slidable on said bed having bearing supportsfor rotatably mounting a pinion on an axis parallel to and movabletoward and away from the axis of said gear supports, cooperating meanson said saddle and said bed for indicating the center distance between agear-set consisting of a gear and a pinion when mounted in therespective supports, cooperating means on said bed and said saddle forpresetting the desired lapped center distance of a gear-set to belapped, said pinion supports consisting of a lower part fixable on thesaddle and an upper part consisting of a pair of coaxially spaced headsfor supporting a pinion rockably mounted on the lower part to permitmovement of the pinion supporting axis through said heads toward andaway from the gear supporting axis of the gear supports, means forapplying an equal predetermined constant force to each of the rockablymounted upper parts to urge the supporting axis of the pinion toward thegear supporting axis and cooperating means on the lower and upper partsof the pinion supports for limiting such rockable movement of said upperpart toward the gear to the pre-setting of the desired center distanceof the gearset to be lapped.

2. A gear lapping machine according to claim 1 wherein the means forapplying an equal predetermined constant force against each of therockably mounted upper parts are fluid pressure operable means.

3. A gear lapping machine according to claim 1 wherein the cooperatingmeans on the lower and upper parts for limiting the rockable movement ofthe pinion comprises a base or wing portion on the upper part engageablewith an overhanging flange on the lower part.

4. A gear lapping machine according to claim 1 wherein the upper headsare independently adjustable.

5. A gear lapping machine according to claim 1 wherein the lower part isformed integral with the saddle.

6. A gear lapping machine comprising a bed, bearing supports on said bedfor rotatably mounting a gear, a saddle movable on said bed toward andaway from said bearing supports, pedestal heads carried by said saddleand having bearing supports for rotatably mounting a pinion on an axisparallel to the axis of the bearing supports for the gear, said pedestalheads being rockable to move the bearing supports thereof toward andaway from the axis of said gear bearing supports, means for maintaininga constant equal pressure on the pedestal head bearing supportstransversely to the axis thereof to urge said axis toward the axis ofthe gear supports, means for limiting the rockable movement of saidpedestal heads toward the axis of the gear supports so that saidlimiting position of the axis of said pinion supports is that of thepinion at the end of a lapping operation of a gear and pinion setmounted in the respective supports, cooperating indicating means on saidbed and on said saddle for indicating the distance between the axes ofthe respective gear and pinion supports when the pinion supports are atthe limit of their rockable movement toward the axis of the gearsupports, and means for moving the saddle toward the gear supports adistance such that when the desired center distance of a gear-set to belapped mounted in the supports in meshing engagement is indicated bysaid indicating means, the pinion supports of the pedestal heads willhave been rocked back from the limiting mean an amount equal to theexcess of the desired center distance of the gear-set before lapping.

References Cited in the file of this patent UNITED STATES PATENTS1,078,570 Aichele Nov. 11, 1913 1,154,830 Alquist Sept. 28, 19151,697,823 Schurr Jan. 1, 1929 1,960,841 Fellows May 29, 1934 1,966,172Jackowski July 10, 1934 2,060,803 Falk Nov. 17, 1936 2,257,989 SykesOct. 7, 1941 2,326,368 Kullman et 'al Aug. 10, 1943 2,385,129 DavisSept. 18, 1945

